1. Field of the Invention
The present invention relates to a wafer having a thermal circuit and a power supplier therefor, and more particularly, to a wafer having a thermal circuit and power supplier therefor, which enable the wafer to be heated or cooled without any additional heating or cooling system.
2. Description of the Related Art
In general, a semiconductor device is fabricated through a plurality of processes including an ion implantation process, a layer deposition process, a diffusion process, and a photolithography process. Among these processes, the photolithography process, which is carried out to form a desired pattern, is an essential process for the fabrication of the semiconductor device.
In the photolithography process, a mask pattern or a reticle pattern is formed on the semiconductor device in order to selectively define a region to be doped and a region to be protected. Conventionally, such a photolithography process includes a coating process in which a photoresist is dropped on the device which rotates at high speed so that the photoresist is coated on the device to a desired thickness, an exposure process in which the device coated with the photoresist and a predetermined mask are aligned to each other and the photoresist coated on the device is irradiated with ultraviolet (UV) rays through the mask so that a mask pattern or reticle pattern is transferred on the device, and a developing process in which the photoresist coated on the device, which underwent the exposure process, is developed to form a desired photoresist pattern.
Furthermore, the photolithography process includes a baking process in which the semiconductor device is baked at a predetermined temperature. Specifically, the baking process can be categorized into a baking process required for removing moisture absorbed on the device before the photoresist is coated, a soft baking process performed after a predetermined organic solvent and the photoresist are coated, and a post-exposure baking (PEB) process required for repairing instability of a chemical structure of an exposed portion caused by the scattering of UV rays during the exposure process.
In order to bake the semiconductor device as described above, a wafer heating system, which is a type of semiconductor fabrication equipment, is used to substantially conduct a wafer baking process in a bake chamber.
A conventional wafer heating system is widely used not only for the above-described photolithography process but also to heat a wafer during a variety of processes. The conventional wafer heating system includes: a flat heating plate, which is installed in close vicinity to a wafer to transmit heat to the wafer; and a heater, which is installed on a bottom surface of or inside the heating plate to heat the heating plate.
Meanwhile, a conventional wafer cooling system, which serves to cool off a heated wafer, includes: a flat cooling plate, which is installed in close vicinity to the wafer to exchange heat with the wafer; and a cooling wafer line, which is installed on a bottom surface of or inside the cooling plate to cool the cooling plate.
However, in the conventional wafer heating system (cooling system), a wafer is mounted on the heating plate (cooling plate), and heater (cooling wafer line) heats (cools) the heating plate (cooling plate) to heat (cool) air near the reverse surface of the wafer. In other words, since the wafer cannot be directly heated (cooled), the heater (cooling wafer line) primarily exchanges heat with the heating plate (cooling plate), the heating plate (cooling plate) secondarily exchanges heat with an air layer near the reverse surface of the wafer, and the air layer near the reverse surface of the wafer thirdly exchanges heat with the wafer. In addition to the multi-step heat exchange process, it is difficult to control heat conduction for each heat exchange process. That is, owing to unstable heat convection in the air layer, it is very difficult to heat (cool) the semiconductor device disposed on the wafer to a desired temperature. Thus, a lot of heating (cooling) energy is wasted so that the system's efficiency is deteriorated. Further, because the conventional wafer heating (cooling) system is separately installed from the wafer and structurally complicated, it takes much time and cost to produce and install the system.
Also, in the conventional wafer heating system or cooling system, the heater is unnecessarily large-sized, a coolant, such as cooling water, is high-priced, and a variety of contaminants are generated, thus polluting the environment.
Meanwhile, a conventional wafer temperature measuring system also cannot precisely measure the amount of thermal energy that acts on the semiconductor device or actual temperature in real time because the system is separately installed from the wafer (e.g., an additional test wafer is used or a sensor is installed in vicinity of a wafer to measure temperature).